1. Field of the Invention
The present invention relates generally to poppet valves, and more particularly to a seat guided poppet valve having improved flow directing characteristics and variable dampening.
2. Description of the Prior Art
The growing necessity for energy conservation, particularly in the area of natural gas reserves, has kindled new interest in developing better ways to transport natural gas and the like more efficiently and at less cost. Generally, gas transmission facilities have relied on reciprocating compressors to move the gas through pipelines connecting the gas reserve to the intended point of use. Many of these compressors utilize poppet valves to provide suction or discharge capability. Inasmuch as these valves may experience up to one thousand closures per minute or more, any deficiency of the valve results in reduced efficiency, excessive wear and possible valve failure.
As is well understood, the poppet element or poppet is a spring-loaded mushroom-shaped pneumatically actuated seal which reciprocates in coaxial bores in a valve seat and a guard or stop. In conventional valves, the poppet is guided by a stem portion in the valve guard. A spring received in a recess or counterbore in the stem serves to provide a return force for initiating the return of the poppet as well as to provide an opposing force to prevent premature and excessively rapid opening of the valve. Generally, a close fit between the poppet stem and the guard is required to provide dampening action.
Such valves have historically experienced manufacturing and maintenance problems, arising from the fact that the poppet head must be accurately positioned with respect to its mating seating surface on the valve seat. Since the poppet is guided in the guard, extremely close tolerances are required to develop the proper mechanical alignment between the seat and guard. For this reason, seats and guards must generally be maintained in matched sets, which complicates routine servicing and prevents renewal of the seat sealing surface without replacement of the entire valve. It has been suggested that additional clearance be provided between the poppet stem and the guard, which had led to unsatisfactory dampening action and poppet seating. Furthermore, these large clearances have generally prevented optimization of valve action for efficient compressor operation through adjustable dampening or variable valve lift.
Efficiency has also been reduced in prior art poppet valves by turbulence created by restrictions in the flow path, which leads to non-uniform flow velocities, losses and unnecessarily large pressure drops. For such compressors, it has been found that any turbulence produces resistance impeding the flow of gas leading to increased component wear.